Coppersmith work started waning in the late 1970s, early 1980s and those in the sheetmetal trade began doing the coppersmith's work, the practices used being similar to those in the plumbing trade. Coppermiths in recent years have turned to pipe work, not only in copper but also stainless steel and aluminum, particularly in the aircraft industry. They are one of the few trades that have a mention in the Bible. (2 Timothy 2:14, Alexander the Coppersmith although later editions mention a metalworker.)

Copper is generally considered to be a soft metal, meaning it can be worked without heating. Over a period of working the metal in this way it can 'work harden'. This means that the molecules within the copper are compressed and irregular in their arrangement. This causes stress in the metal and eventually cracking the metal along these stress points. In order for the copper to be worked to any extensive degree it must be annealed. This process involves heating the metal and then rapidly cooling it in water. The cooling stage is known as quenching. By heating the copper, the molecules in the metal are relaxed, and able to align themselves in a more uniform fashion. This allows for easier shaping of the metal. In order to keep this uniformity within the metal, it is cooled instantly. This prevents the molecules from moving around and causing tension in the structure of the metal.

References

Fuller, John. The Art of Coppersmithing: A Practical Treatise on Working Sheet Copper into all Forms. Mendham, NJ: Astragal Press, 1993. (reprint of the original 1894 edition). ISBN 1879335379